<!DOCTYPE html>
<html>

<head>
  <meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
  <title>Hello, World</title>
  <style type="text/css">
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }

    #allmap {
      height: 100vh;
    }
  </style>
  <script type="text/javascript" src="http://api.map.baidu.com/api?v=3.0&ak=ijCGWdrska19tHRFRtN6fy49kNV10eUC"></script>
</head>

<body>
  <div id="allmap"></div>
  <script type="text/javascript">
    var map = new BMap.Map("allmap");
    var point = new BMap.Point(116.331398, 39.897445);
    map.centerAndZoom(point, 12);

    function myFun(result) {
      var cityName = result.name;
      map.setCenter(cityName);
      alert("当前定位城市:" + cityName);
    }
    var myCity = new BMap.LocalCity(); 
    myCity.get(myFun); 
  </script>
</body>

</html>